Distillation of aviation gasoline components



May 12, 1953 J. G. BROWDER 2,633,412

DISTILLATION OF AVIATION GASOLINE QOMPONENTS Filed April 14, 1951PENTANES AND LIGHTER OXIDA TION INHIBITOR I FRACTIONA TION ZONE AVIATIONGASOLINE COMPONENT INVENTOR.

Patented May 12, 1953 DISTILLATION OF AVIATION GASOLINE COMPONENTS JohnG. Browder, Houston, Tex., assignor, by

mesne assignments, to Standard Oil Development Company, Elizabeth, N. Ja corporation of Delaware Application April 14, 1951, SerialNo. 221,092

4 Claims.

The present invention is directed to the distillation of aviationgasoline components. More particularly, the invention'is concerned withthe distillation of a hydrocarbon fraction containing -olefins'which issusceptible to formation of gum on exposure of the fraction to anelevated temperature such as encountered in distilling same.

The present invention may be briefly described as involving the recoveryof a higher boiling fraction from a mixture of same with a lowerboilingfraction which involves distilling an olefinic hydrocarbon fractionhaving a boiling point no greater than 300 F. and susceptible toformation of gum therein on exposure to elevated temperatures in thepresence of at least 0.01

pound of an oxidation inhibitor per 1000 gallons of said fraction toremove as an overhead fraction hydrocarbons boiling below 100 F. andrecovering as a bottoms fraction gum stable higher boiling fractionscontaining said inhibitor.

The feed stock of the present invention may be a paraffinic and aromaticfraction which is ene diamine and N,N'-di-sec. butyl-p-phenylenediamine.

In the practice of the present invention it is to be emphasized that theoxidation inhibitor is added to the fraction to be distilled and not tothe distilled fraction. If the inhibitor is added to the distilledfraction undesirable results are obtained.

The invention will be further illustrated by reference to the drawing inwhich the single figure is a flow diagram of the preferred mode.Referring now to the drawing, numeral ll designates a charge tank. inwhich abody of a hydrocontaminated to a slight extent with olefinss Thisfraction has a boiling range from about 85 to about 300 F. The feedstock of the present invention maybe recovered by distilling selectedcrude petroleum or it may be formed in certain catalytic conversionoperations such as hydroforming operations. A preferred feedstock of thepresent invention is a fraction recovered from a hydroforming operationwhich boils in the range from about 85 to about 200 F. and whichcontains about 3.0% by volume of olefins. This fraction ispredominantlyparaflinic but may contain 20% by volume of aromatics.Ordinarily such a fraction'will contain aromatics in the range from 10%to about 20% by volume.

The oxidation inhibitor which is added to the olefin-containinghydrocarbon fraction prior to distilling same is preferably an alkylatedmonohydroxy phenol. Suitable mono-hydroxy phenolsi have been disclosedin the patent literature and particularly in U. S. 2,202,877, issued toStevens and Gruse. mono-hydroxy phenols are the tri-alkylatedmono-hydroxy phenols, such as 2,4,6-tri-tertiary- Particularly desirablealkylatedj" butyl-phenol, 2,4 di methyl 6 tertiary-amyl-4-methyl-phenol. Particularly useful as an oxidation inhibitor in thepresent invention is a 2,6 di tertiary butyl 4 methyl phenol.

This latter compound is particularly useful when carbon fraction havinga boiling point no greater than 300 F. is maintained. Such fraction maybe. a hydroformed fraction boiling in the range from about to 200F. Thefeed stock is withdrawn from tank II by line 12 containing pump l3 andis discharged thereby into a fractionation zone I4. Fractionation zone Mmay be'a single fractionation tower or a plurality of fractionatingtowers but for convenience of description is shown as a single tower. Itis understood that fractionation zone M will be provided with suitableinternal baffiing equipment, such as bell cap trays and the like, toinsure intimate contact between vapors and liquids to allow a sharpseparation in the fractionation zone It. Fractionation zone I4 isprovided with line R5 for removal of an overhead fraction and line l6for recovery of a bottoms fraction. Fractionation zone It is alsoprovided with a heating means illustrated by a steam coil I! foradjustment of temperatures and pressure therein.

The feed stock of the present invention prior to introduction in thefractionation zone M has injected thereinto by line [2 an inhibitingamount of an oxidation inhibitor by way of line 18. The oxidationinhibitor employed may suitably be one of the type illustrated beforeand is used in an amount in the range between 0.01 and 0.5 pound ofoxidation inhibitor per 1000 gallons of feed stock.

In practicing the present invention, the inhibited feed stock issubjected to distillation conditions to remove overhead fractionsboiling below about F. which will include pentanes and lighter which maysuitably be used for adjustment of vapor pressure in hydrocarbonfractions having a deficient volatility. The desired fraction containingthe oxidation inhibitor is recovered by line l6 and may suitably be usedas an aviation gasoline component. This fraction is gum stable and hasnot formed in it gum components as a result of the high temperaturesprevailing in fractionation zone [4. Such temperatures for distilling astock, such as illustrated having a final boiling point of about 200will be around about 145 F.

In order to illustrate the invention further a light fraction obtainedfrom a hydroforming op- Table iii-Hr. Stock Acc.

Gum

Charge to Still 0.0 Bottoms from Still (Inhibitor added immediatelyafter distillation) 26. 4 Bottoms from Still (Inhibito'r added to chargeto still) 1. 4

It will be seen from the data that the 16-hour accelerated gum test ofthe bottoms fraction which was inhibited after distillation was 26.4,whereas in the practice of th present invention the 16-hour acceleratedgum test was only 1.4. From the foregoing data-it is believed apparentthat the practice of the present invention allows markedly superiorresults to be obtained. In fact, the practice of inhibiting the bottomsprodnot after distillation rather than before, due to the highaccelerated gum values, which averaged from to 50 milligrams per 100millilitersof sample, had to be discontinued. These high values areunacceptable for components of aviation gasoline. On the other hand, thevalue of 1.4 milligrams per 100 milliliters of sample is entirelyacceptable and the bottoms fraction so recovered in the practice of thepresent invention may suitably be used in aviation gasoline as ablending component thereof.

The accelerated gum test is determined in accordance with the A. S. T.M. Procedure D 873-49.

The amount of olefins in the feed stock of the present invention issmall but apparently enough to contribute a susceptibility to formationof gum on activation by heat at the temperature prevailing duringdistillation. The bromine number of the stocks utilized ranged fromabout 1 to 6. The stock given in the foregoing examples had a brominenumber of 5. A description of the bromine number test may be found in A.S. T. M. Procedure D-875-46T.

It is to be emphasized that the present invention is directed to therecovery of components which may be used in aviation gasoline and hasnothing to do with the inhibition during distillation of polymerizablecomponents, such as butadiene, styrene, and the like.

. The nature and objects of the present inven tion'having beencompletely described and illustrated, what I wish to claim as new anduseful and to secure by Letters Patent is:

1. A method for recovering a higher boiling fraction from a mixture ofsam with a lower boiling fraction which comprises adding an alkylatedmonohydroxy phenol oxidation inhibitor,'in an amount in the rangebetween 0.01 and 0.5 pound per thousand gallons, to a convertedhydrocarbon fraction consisting of a predominant amount of saturatedhydrocarbons, a lesser amount of aromatic hydrocarbons, and a stilllesser amount of olefinic hydrocarbons and boiling in the range betweenand 300 F. and susceptible to formation of gum therein on exposure to anelevated temperature within said boiling range, distilling, saidinhibited hydrocarbon fraction to form an overhead fraction boilingbelow F. and a gum stable bottoms fraction containing said inhibitor,and recovering said bottoms fraction as a component of aviationgasoline.

2. A method in accordance with claim 1 in which the oxidation inhibitoris 2,6-di-tertiarybutyl-4-methy1 phenol.

3. A method in accordance with claim 1 in which the fraction susceptibleto gum formation is a hydroformed fraction boiling in the range between85 and 200 F.

4. A method for removing pentanes and lighter fractions from ahydrocarbon fraction susceptible to formation of gum on exposure of sameto an elevated temperature which comprises distillinga hydroformedfraction consisting of a predominant amount of saturated hydrocarbons, alesser amount of aromatic hydrocarbons, and a sti11 .lesser amount ofolefinic hydrocarbons and boiling in the range between 85 and 200 F. inthe presence of 0.1 pound of 2,6-di-tertiarybutyl-4-methyl phenol perthousand gallons of said hydroformed fraction at a temperature nogreater than F. to remove as an overhead fraction pentanes and lighterand recovering as a bottoms fraction gum stable higher boiling fractionscontaining said inhibitor as a component of aviationgasoline.

JOHN G. BROWDER.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,181,102 Stoesser et a1 Nov. 21, 1939 2,202,877 Stevens et alJune 4, 1940 2,240,764 Dreisbaeh et al. May 6, 1041 2,257,079 StorySept. 23, 1941 2,526,963 Morris Oct. 24, 1950

4. A METHOD FOR REMOVING PENTANES AND LIGHTER FRACTIONS FROM AHYDROCARBON FRACTION SUSCEPTIBLE TO FORMATION OF GUM ON EXPOSURE OF SAMETO AN ELEVATED TEMPERATURE WHICH COMPRISES DISTILLING A HYDROFORMEDFRACTION CONSISTING OF A PERDOMINANT AMOUNT OF SATURATED HYDROCARBONS, ALESSER AMOUNT OF AROMATIC HYDROCARBONS, AND A STILL LESSER AMOUNT OFOLEFINIC HYDROCARBONS AND BOILING IN THE RANGE BETWEEN 85* AND 200* F.IN THE PRESENCE OF 0.1 POUND OF 2,6-DI-TERTIARY-